Browsing by Author "Martinez, P"

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    Cloning and comparison of ten gene sequences of a Chilean H-pylori strain with other H-pylori strains revealed higher variability for VacA and CagA virulence factors
    (2002) Müller, I; Medina-Selby, A; Palacios, JL; Martinez, P; Opazo, P; Bruce, E; Mancilla, M; Valenzuela, P; Yudelevich, A; Venegas, A
    We have cloned and sequenced ten Helicobacter pylori genes from a Chilean strain (CH-CTX1) including: a cytotoxin VacA fragment, a CagA fragment (A 17), a species-specific protein (TsaA), urease subunits (UreA, UreB), a flagellin subunit (FlaB), heat shock proteins (HspA and HspB), adhesin (HpaA) and a lipoprotein (Lpp20). We compared their deduced amino acid sequences with the corresponding sequences from three unrelated H. pylori strains, including fully sequenced strains 26695(UK) and J99(USA), and found that eight of them (UreA, UreB, FlaB, HspA, HspB, Lpp20, TsaA and HpaA) presented more than 97.3% identity. In contrast, VacA partial sequence showed lower identity values (93.2-94.9%). Moreover, we found major differences in the A] 7 region respect to the number and arrangement of the internal repeated elements when sequences from different strains were aligned. The A17 regions from strains CH-CTX1 and 26695 are very similar (91.8% identity) but lacked 6 repeated elements when compared to the Australian strains ATCC 43526 and NCTC 11637. The CCUG 17874 A17 region showed the largest deletion involving 9 repeats. A 17 size differences between strains CCUG 17874 and CH-CTX1 were verified by PCR and polypeptide size. Such differences may explain variations in virulence among H. pylori strains as well as diversity in serum immunoreactivity.
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    Diversity, flower visitation frequency and generalism of pollinators in temperate rain forests of Chiloe Island, Chile
    (2005) Smith-Ramírez, C; Martinez, P; Nuñez, M; González, C; Armesto, JJ
    Species richness and taxonomic composition of pollinator assemblages are documented for 26 plant species from temperate rain forests of northern Chiloe Island, southern Chile (42 degrees 30'S). We investigated the patterns of generalism and specialization among plants and animal pollinators by comparing the flower visit frequency by different pollen vectors during the spring and summer months of three consecutive years (2000-2002). Species studied exhibited a range of floral morphologies (radial vs. zygomorphic, open vs. tubular) and rewards (nectar and/or pollen). Overall, we recorded 172 pollinator species, with an average of 6.6 species of pollen vectors/plant species. Pollinators visited an average of 15.2 plant species/pollen vector. Pollinator assemblages were dominated by Coleoptera (75 species), Diptera (56 species) and Hymenoptera (30 species), but passerine birds and hummingbirds were also important. The most specialized plants were vines, including the bee-pollinated genus Luzuriaga (Philesiaceae) and two endemic species of hummingbird-pollinated Gesneriaceae. Hymenoptera contributed 41.2% of all visits, with the bumblebee Bombus dalhbomi accounting for 22.5% of these. Plants with unspecialized flower morphology supported a higher species richness of pollinators, but visiting rates did not differ from specialized flowers. 2005 The Linnean Society of London, Botanical Journal of the Linnean Society.
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    Persistent hypokalemia after successful adrenalectomy in a patient with Cushing's syndrome due to ectopic ACTH secretion
    (1999) Arteaga, E; Fardella, C; Campusano, C; Cárdenas, I; Martinez, P
    Ectopic ACTH secretion is characterized by a high incidence of hypokalemia. The pathophysiology of hypokalemia has not been totally clarified, although it has been postulated that excessive amounts of adrenal steroids may play a role, as well as a possible role of the inhibition of the enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD). This enzyme normally converts cortisol to cortisone avoiding the mineralocorticoid action of cortisol. We present a patient with ectopic ACTH secretion due to a metastatic carcinoid tumor. The clinical picture was characterized by maintained hypokalemia (1.4 mmol/l) resistant to potassium, spironolactone and ketoconazole administration. A bilateral adrenalectomy was performed but the hypokalemia persisted while he was receiving a physiological dose of cortisol. Eight days after adrenalectomy cortisol was replaced by an equivalent dose of dexamethasone. This change was followed by a rapid and persistent normalization of hypokalemia suggesting a mineralocorticoid effect of cortisol. In conclusion, the origin of hypokalemia in our patient with ectopic ACTH secretion was secondary to cortisol. We postulate that this peculiar effect of cortisol could have happened if an inhibition of 11 beta-OHSD occurred. (J. Endocrinol. Invest. 22: 857-859, 1999) (C) 1999, Editrice Kurtis.